Figure 1

(a) Schematic of the device. Contacts $A$ and $B$ are partially under the top gate. Under certain values of $V_T$ and $V_B$, a PNJ forms (black dashed line), connecting contacts $A$ and $B$. The change of the Lorentz force due to the carrier sign change creates a snakelike trajectory between the two contacts. (b) False-color image of a device similar to the one studied. (c) The signature of the additional conduction is a reduction of resistance parallel to the junction: for four-terminal resistance measured parallel to the PNJ, $R_{\mathrm{odd}}$ (defined in the text) is negative (black trace), whereas the four-terminal resistance measured perpendicular to the junction yields a positive $R_{\mathrm{odd}}$ (blue trace).Reuse & Permissions

Figure 2

Four-terminal resistances $R_{xx}$, $S_{xx}$, $R_{xy}$ and $S_{xy}$ as a function of top-gate voltage $V_T$ (offset for clarity) for $B$ between $\pm 2\mathrm{T}$ in 0.5 T steps at a back-gate voltage of $-20\mathrm{V}$. Upper inset shows measurement, with black (gray) contacts as current (voltage) leads. (a) $R_{xx}(V_T)$. The red dashed line locates the resistance maximum at all $B$ fields and indicates the CNP for Region  1. Lower inset: $R_{xx}(V_T,B)$ shows that the CNP does not change over the $B$ range explored. (b) $S_{xx}(V_T)$. A drop in resistance of $0.3–0.5\mathrm{k}\Omega$ is observed at the transition from the $p\mathrm{\text{−}}p$ regime to the $p\mathrm{\text{−}}n$ regime (red dashed line), indicating that an additional conduction channel has been introduced at the $p\mathrm{\text{−}}n$ interface. Resistance drop occurs for the full B range (lower inset). (c) Hall resistance $R_{xy}(V_T)$ with all the contacts under top gate is antisymmetric with respect to the CNP. (d) In contrast, $S_{xy}$ (d) has larger resistance on the $p\mathrm{\text{−}}n$ side of the CNP indicating an additional conduction channel at the $p\mathrm{\text{−}}n$ interface. (e) The additional resistance, $S_{xy}\mathrm{\text{−}}{R}_{xy}$ is maximal in the bipolar regime for all $B$ (lower inset).Reuse & Permissions

Figure 3

(a)–(c) Schematic of edge-state transport in the quantum Hall regime for ${\nu }_{R2}=-10$, and ${\nu }_{R1}$ ranging from (a) 2, (b) the transition from 2 to 6, and (c) 6. At the transition between 2 and 6, snake states enhance $S_{xy}$ in a manner similar to Fig. 2, with an amplitude that increases as $B$ increases. (d) $S_{xy}(V_T,B)$ reveals expected plateaus of $1/10$, $1/6$ and $1/2$ $h/e^2$ in the unipolar regime ($V_T<4\mathrm{V}$) and deviations from these values in the bipolar regime. An enhanced value of $S_{xy}$ is observed at the transition between ${\nu }_{R1}=2$ and 6 and is attributed to the presence of snake states at the $p\mathrm{\text{−}}n$ interface. (e) Constant $B$-field cuts of (d) for $B$ between 0 and 8 T in 2 T steps. Cuts from 0 to 6 T are shifted downward from the $B=8\mathrm{T}$ cut for clarity.Reuse & Permissions

Figure 4

$\Delta V$ dependence of the difference $S_{xy}\mathrm{\text{−}}{R}_{xy}$, plotted on a log scale, for $B$ between 0 and 2 T in 0.5 T increments. $S_{xy}\mathrm{\text{−}}{R}_{xy}$ is reduced as $\Delta V$ becomes larger for all $B$ fields. Solid black lines are guides to the eye. The decrease in resistance in this $\Delta V$ range increases as the perpendicular field is increased, rising from $\sim 0.2\mathrm{k}\Omega$ at $B=0\mathrm{T}$ to $\sim 1\mathrm{k}\Omega$ at $B=2\mathrm{T}$.Reuse & Permissions